There is a need for a precise pressure regulating device which can control fluid pressures at very low levels, for example in the range of body cavity or arterial or venous pressures. Further, it would be useful if such a regulator could be controlled automatically through a remote pressure signal. Further, there is a need for such a regulator to be hygienic and made from medically compatible and approved materials. All components of such a device which come into contact with bodily fluids should further be either disposable or autoclavable. There is also need for a small disposable precision regulator that can be used to control critical fluid flows such as medicine, bile, plasma, saline solution and blood, internally and externally; locally and over a broad region of a patient's body.